1. Field of the Invention
The present invention relates to the field of integrated power supply circuits. More specifically, the present invention relates to the integration of a component belonging to the ignition circuit of a two-stroke motor.
2. Discussion of the Related Art
FIG. 1 is a partial simplified equivalent electric diagram of an ignition circuit for a two-stroke motor.
The circuit comprises, between two input terminals E and REF, an inductive winding L1 periodically excited by the passing of a magnet, not shown, arranged on a wheel which is set to motion with the crankshaft when the motor is desired to be started.
A terminal A is connected to a first positive armature of a capacitor C. A second negative armature of capacitor C is connected to a terminal K via a primary winding N1 of a magnetic circuit having a secondary winding N2 providing a high voltage to a circuit for igniting a two-stroke motor, the structure of which is not described in detail.
Terminals REF and K are interconnected to correspond to a low reference terminal of the circuit.
Between terminal E and terminal A, the circuit comprises a diode D2 only conducting the current from terminal E to terminal A.
A normally-off one-way switch controllable to be turned on is connected between terminal A and terminal K. For example, the normally-off switch is a thyristor Th having its cathode connected to terminal K. Gate G is connected to a control circuit DRIVE capable of providing a turn-on control signal.
A free-wheel diode D3 is connected between terminals A and K in anti-parallel with respect to thyristor Th.
A diode D1 is connected between terminals E and REF, its anode being connected to terminal REF. Cathode F of diode D1 is connected to terminal E via a resistor R.
The operation of the circuit of FIG. 1 is the following.
On passing of the magnet close to winding L1, the magnetic flow variation causes the occurrence of a current pulse. The displacement direction of the magnet and the winding direction of coil L1 is such that the pulse charges capacitor C through diode D2. Diode D1 and resistor R are used to absorb a possible negative current between terminals E and Ref.
Capacitor C and winding L1 are sized so that a single passing of the magnet close to winding L1 causes a sufficient current pulse to charge capacitor C to a required maximum voltage level.
The magnet also passes in front of a winding, not shown, forming the power supply of control circuit DRIVE of thyristor Th. The location and the dimensions of this winding are such that thyristor Th is controlled to be turned on while capacitor C has reached the maximum voltage level.
Then, capacitor C discharges into the circuit formed of capacitor C, primary winding N1, and the conduction path of thyristor Th. This circuit is an oscillating circuit and the negative halfwaves pass through free wheel diode D3. This results in the occurrence of a high voltage across secondary winding N2.